It is known that light-emitting diodes (LEDs) are used as a radiation-emitting component in many different fields of applications of novel light sources in order to benefit from the longer service life and better energy efficiency compared with conventional lighting means. Thus, examination or operating lights increasingly use LED technology, especially white LEDs. White LEDs may be composed of a blue-emitting semiconductor, which is coated with a phosphor layer, which absorbs part of the transmitting blue light, fluoresces broad-band yellow light and thus generates white light by mixing the radiation.
In addition, some basic properties of operating lights, e.g., the color temperature or light color, which must be met by operating lights, are specified in International Standard IEC 60601-2-41 entitled “Medical Electrical Equipment—Part 2-41: Particular requirements for the basic safety and essential performance of surgical luminaires and luminaires for diagnosis”.
Thus, a color temperature of 3,000 K-6,700 K is specified within a “color hexagon” close to the black body line for operating lights according to this standard specification. A light color temperature of about 4,500 K is established for operating lights (similar to direct sunlight).
The LED technology in operating lights makes it possible to directly set a color temperature (Correlated Color Temperature (CCT)) of the white light, e.g., by setting the properties of the phosphor material and setting the absorption length over the layer thickness of the phosphor material, for example, with monochromatic white LED with a color temperature of 4,500 K. As an alternative, this can likewise be achieved with different colored LEDs or different white LEDs. Light is mixed here to white at the site of the focus. An adjustable color temperature is likewise possible in operating lights of the LED configuration mentioned in the alternative, and this is set mostly according to personal preference.
An operating light with a plurality of LED lighting means is known from EP 1568936 A1, wherein some LEDs are designed to produce colored light and other LEDs are designed to produce white light and means for setting the intensity of the colored LEDs are provided. Furthermore, a process for lighting an operating site with an operating light comprising white or colored LEDs is described, wherein the intensity of the colored LEDs is adjustable.
An operating light with a light body for receiving lighting means is described in EP 1568934 A1, wherein a light source in the center of the light body can be actuated independently from other lighting means.
WO 2003/019072 A1 shows a conventional white light-emitting diode, which is used to set a color temperature and a color rendering property. The white light-emitting diode sets the color temperature, and a monochromatic correcting light-emitting diode is used to change the color rendering by color mixing.
WO 2007/014769 A1 shows an operating light with at least one light source arranged in a light body and with an optical means. To direct the visible radiation of the light source in a main light emission direction onto a field of operation, the operating light has an auxiliary lighting means, which can be switched independently from the light source.
An operating light, which has an optical imaging system and at least one lighting element with at least two light sources, wherein the light sources emit emissions of different spectra, is known from EP 1985912 A1. The light sources are arranged close to the optical axis of the lighting element, so that the emissions are superimposed even before they reach a reflector.
It is known that light with a large blue component (white light with a higher color temperature above 4,000 K, also called cold white or neutral white) enhances the ability to concentrate and reduces fatigue. However, this light is often felt to be too glaring and cold. Light with a large red component (lower color temperature below 4,000 K, warm white) is, by contrast, helpful for relaxing and relieves stress.